1. Field of the Invention
The present invention relates to a membrane and to a method for the production of the same, and here particularly to a membrane with corrugation grooves and antistick elements as well as to a method for producing the same. Particularly, the present invention relates to a membrane for a microphone, for example a silicon microphone.
2. Description of the Related Art
The center element of a micromechanically realized silicon microphone is the membrane used therein, which is to vibrate in the sound field. One prerequisite for this membrane is that it is as sensitive as possible, but it may not stick to the counter electrode in strong deflections and a resulting contact with the counter electrode. Such strong deflections are caused, for example, by high sound levels, an electrostatic attraction or the surface tension of fluids.
In the prior art, several approaches are known to improve, on the one hand, the sensitivity of the membrane and to avoid, on the other hand, sticking of the membrane.
One approach for optimizing the sensitivity is to optimize the layer properties and the lateral design of the membrane, for example by so called spring membranes. However, this approach is disadvantageous in that the reduced area of the membrane resulting from the optimization also lowers the capacity of the membrane.
A further approach for improving the sensitivity of a membrane for a silicon microphone is to provide so-called corrugation grooves in the membrane. One such approach is described, for example, by Zou, Quanbo et al. in “Design and Fabrication of Silicon Condenser Microphone Using Corrugated Diaphragm Technique” in Journal of Microelectromechanical Systems, Vol. 5, No. 3, September 1996. According to this approach, V-shaped trenches are formed in a silicon substrate to generate the desired corrugation grooves in the subsequent formation of the membrane.
One approach for avoiding an irreversible sticking of the membrane to a counter electrode is to produce so called antistick elements (antistick bumps/dimples). These antistick elements are needle-type structures in the membrane, which reduce the contact region during contact with the counter electrode significantly, as it is described by Brauer, et al. in “Silicon Microphone Based on Surface and Bulk Micromachining”, Journal of Micromechanics and Microengineering, 11 (2001), pp. 319-322. It is the disadvantage of this approach that the production of the needle-type structures means additional process effort.
With regard to the solutions known in the prior art, it has to be noted that they teach independent processes, on the one hand for generating the antistick elements and, on the other hand, for increasing the sensitivity of the membrane.